Time, Space, and Matter
by Fool of Diamonds
Summary: What sort of shenanigans can two seemingly all-powerful immortal beings get into? Apparently a lot, especially when the two are "getting into" each other while they're at it. Mephisto and an OC, as well as Amaimon and an OC later. Rated M for Shenanigans of the sexy kind.
1. Graveyard Deals

**Hi I don't own Blue Exorcist I only own my original characters and the idea to this fic thanks bye.**

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It was a downcast day, with the sky more like a large expanse of rainclouds thick and heavy.

Fat raindrops fell steadily, but the lone figure standing in the graveyard knew that it would soon fall in sheets.

Even so, not a drop dared drench them as they stood, neck craned downward to stare at a tombstone.

"Mountains fall, rivers rise." They spoke. "And even you had to fall at some point, Shiro."

"Unlike you, of course." A voice spoke behind them.

They didn't even move to greet him or jump in surprise- they knew he was there.

"I did my falling millennia ago." They replied. "But of course, you already know that, Mephisto."

Finally, they turned, still having to look down, but instead of looking down at a tombstone, they looked down on a rather oddly dressed man with a pink umbrella shielding him from the rain.

"Not the details, no. You never shared those with me, Mr. Hershel." Mephisto mentioned, grinning devilishly at the taller person.

Mr. Hershel chuckled, cracking a smile.

"I suppose I never did. It's a rather boring story, in my opinion."

They closed their eyes for a moment, bringing their head up, before opening their eyes once more to look up at the sky.

"Now then, I highly doubt you'd come here just to chat about me." Hershel began. "Your half-brothers and your plans for them are far more interesting and compelling."

Mephisto' grin widened, but he said nothing just yet.

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Hershel finally looked back to Mephisto, dark brown eyes locking with his emerald green ones in a piercing stare.

"I'm curious to see how this little game will play, so I will willingly enter myself into these...shenanigans." They consented to an unasked question, lips curving into a smirk.

Mephisto looked to have split his face in two with the grin he was sporting, and was about to say something, when Hershel spoke once more.

"However, I, unfortunately, have other duties to attend to." They frowned for a moment, before grinning. "Unless we can work something out, hmm?"

"I'm intrigued! Whatever has the great Jewel Box, Kappa Crucis, so very busy that they can't come and play?" Mephisto exclaimed, green eyes flickering with interest.

"Oh, you know." Said Hershel. "Just some brat that I ended up getting custody of. We can call him Gure for now. He's a bit old for your school, but perhaps the cram school can take him in. He's a bit frail at the moment, but once we feed him and care for him, he will blossom like a blue rose."

"Go on." Mephisto goaded.

"He's about 18 now, scrawny thing. A rather pathetic descendant of my people, but even so, he had potential." Hershel added in.

"Well then~" Mephisto purred out. "I'm certain he will make an outstanding exorcist. I'll be happy to take him in under my wing."

Hershel's smirk widened.

"I suppose we'll see you again real soon, Mephisto. Until then~" Hershel bid the demon adeiu, and turned to walk away.

"Oh, and before I forget." Hershel added, stopping in their tracks, turning slightly towards Mephisto. "He _**hates**_ anything to do with the church."

And with that, he left, leaving the demon king behind to think about the pandemonium which would occur soon.

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 **Hershel AKA Jewel Box AKA Kappa Crucis is genderless and usually goes by "they" pronouns, but doesn't mind "he" pronouns. They will also be banging Mephisto soon. Gure will probably bang Amaimon later maybe.**


	2. Business and Pleasure

Hershel stood in Mephisto's office, looking out the windows.

"Art teacher, is it? With little Gure as my assistant?" Hershel questioned.

"Along with Demonology cram teacher, yes." Mephisto confirmed before taking a sip of his tea.

Hershel then turned to Mephisto, face set in seriousness as they looked down at the demon.

"Should I change my appearance? Rather, should I change my height?" They asked.

Mephisto almost choked on his tea, spluttering out a, "What?!"

"Well, I only made myself this tall because I kinda enjoy being taller than you, but it might attract too much attention to myself. Of course, so does the rest of my appearance in Japan, but I'd rather not change that. So, what do you think?" Hershel clarified, brow furrowed.

Mephisto put down his tea cup and saucer, resting them on his desk before standing up and walking towards Hershel.

His gloved hands pressed against Hershel's chest, sliding up to their broad shoulders before sliding back down to their chest, and to the sides, humming appreciatively.

"I think I rather like you like this~" He purred as he gazed up at the taller person.

Hershel grinned wolfishly, their hands reaching down to rest on Mephisto's hips, caressing them through his pantaloons.

"Is that so?"

Mephisto hummed an affirmative response before leaning in for a kiss, Hershel gladly meeting him halfway, and deepening it, groaning in pleasure.

"It's been far too long, my dear~" Mephisto murmured, returning for another kiss.

His fangs grazing Hershel's lips, summoning out a pleased growl from them.

"We'll have to be careful, what with the Vatican and their bullshit." Hershel growled out in between kisses, leaning in more, to reach their lover's neck.

"And whatever would they be able to do to you? You're not human or demon." Mephisto spoke between sighs and moans of pleasure as Hershel nipped, kissed, and sucked at his neck.

"Even so, it can be annoying. It'd probably set the brat off, as well, and I'd much rather not deal with his rage." Replied Hershel as they started removing Mephisto's clothes.

As an after thought, they snapped, causing the windows to be shielded from their activities, darkening the room.

They lifted Mephisto up into his desk, never once removing their lips from his flesh, trailing kisses farther down as more skin was exposed.

"You'll have to tell me more about this young man later." Mephisto said while tugging away at Hershel's unbuttoned shirt, exposing more coppery skin.

Hershel hummed in agreement...

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 **Whoop whoop the rest is shitty gay office sex that I might upload onto Ao3 if people wanna read my horribly written smut.**


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